Undercarriage for a Working Machine

ABSTRACT

An undercarriage for a working machine comprising a main chassis and a subsidiary chassis. The main chassis has a mounting arrangement to mount a superstructure thereon and a mounting interface to mount the subsidiary chassis thereon and the subsidiary chassis has a mount for an axle.

FIELD OF THE INVENTION

The present invention relates to an undercarriage for a working machine,a working machine having an undercarriage and to a method of assemblingan undercarriage of a working machine.

BACKGROUND OF THE INVENTION

Various types of working machines are known. Such machines are usedtypically for soil-shifting operations (e.g. trenching, grading, andloading) and materials handling (e.g. depositing aggregate in trenches,lifting materials and placing them on an elevated platform).

Such machines are typically manufactured from a set of subassembliesdesigned specifically for one type of machine, although certaincomponents such as engines, gearboxes, hydraulic pumps andundercarriages may be shared across different machine types.

Examples of known machines include the following:

Slew excavators comprise a superstructure rotatable in an unlimitedfashion relative to an undercarriage. The superstructure includes aworking arm arrangement for manipulating an attachment, such as abucket, to perform working operations of the type listed above, a primemover, such as a diesel IC engine, a hydraulic pump, and an operatorcab. The prime mover drives the hydraulic pump, in order to providepressurized fluid to operate the working arm arrangement, and also topower one or more hydraulic motors located in the undercarriage that areused to selectively drive either two endless tracks or four wheels (oreight wheels in a dual wheel configuration) for propelling theexcavator.

A slew ring rotatably connects the superstructure and undercarriage, anda central rotary joint arrangement enables hydraulic fluid to pass fromthe pump in the superstructure to the hydraulic motor, and return to thesuperstructure, irrespective of the relative positions of thesuperstructure and undercarriage. If the slew excavator uses tracks forpropulsion, steering is effected by differentially driving the tracks onopposing sides of the undercarriage. If the slew excavator uses wheelsfor propulsion, a steering arrangement is used for either two or fourwheels, and separate hydraulic control is required for this in theundercarriage.

Slew excavators are available in a wide range of sizes. Micro, mini andmidi excavators span an operating weight range from around 750 kg up toaround 12,000 kg and are notable for typically having a working armarrangement that is capable of pivoting about a substantially verticalaxis relative to the superstructure by using a “kingpost” interface tothe superstructure. Generally, mini and midi excavators have a weight ofabove around 1,200 kg. Large excavators, whose operating weight exceedsaround 12,000 kg are often referred to as ‘A frame’ excavators andtypically have a working arm arrangement that is fixed about a verticalaxis, and can therefore only slew together with the superstructure. Thisis a function of the fact that the smaller excavators are expected tooperate in more confined spaces and the ability to slew about twomutually offset axes in order to, for example, trench close to anobstacle such as a wall is therefore more desirable for micro, mini andmidi excavators.

The working arm arrangement generally includes a boom pivotallyconnected to a dipper. There are several types of booms availableincluding: a triple articulated boom which has two pivotally connectedsections; and a mono boom that is often made from a single generallycurved structure. A dipper is pivotally connected to the boom and amount for an attachment, e.g. a bucket, is provided on the dipper.Hydraulic cylinders are provided to move the boom, dipper and mountrelative to each other so as to perform a desired working operation.

Tracked excavators are not able to travel under their own propulsion forsignificant distances due to a low maximum speed and the damage theirmetal tracks cause to paved roads. However their tracks enhance thestability of the excavator. Wheeled excavators are capable of “roading”at higher speeds (typically up to 40 kph), and without appreciablydamaging paved road surfaces. However, the working arm assemblyinevitably extends forward of the superstructure during roading, whichcan impair ride quality, and forward visibility. When performing workingoperations the pneumatic tires provide a less stable platform thantracks, so additional stabilizer legs can be deployed for stability.

Since the prime mover, hydraulic pump, hydraulic reservoir etc. arelocated in the superstructure, the center of gravity of all types ofslew excavator is relatively high. Whilst these components can bepositioned to act as a counterbalance to forces induced during workingoperations, packaging constraints may force such positioning to besub-optimal, and may also restrict sight-lines over the rear of themachine, for example.

Excavators are generally used for operations such as digging. However,if it is desired to perform an operation such as loading, an alternativetype of machine must be used. Machines capable of loading operations areknown and have various formats. In one format, commonly referred to as a“telescopic handler” or “telehandler”, the superstructure andundercarriage are fixed relative to each other and a central working armin the form of a two or more part telescopic boom extends fore-aft ofthe machine. The boom pivots about a horizontal axis towards the aft endof the machine, an attachment is releasably mounted to a fore end of theboom, and is pivotable about a second distinct horizontal axis. Commonlyused attachments include pallet forks and shovels. Telehandlers may beused for general loading operations (e.g. transferring aggregate from astorage pile to a required location on a construction site) and liftingoperations, such as lifting building materials on to an elevatedplatform.

Telehandlers typically have four wheels on two axles for propulsion,with one or both axles being steerable and driven. A prime mover(typically a diesel IC engine) may be located in a pod offset to oneside of the machine between front and rear wheels and is connected tothe wheels by a hydrostatic or mechanical transmission. An operator cabis often located on the other side of the boom to the prime mover, andis relatively low between the wheels. Depending upon its intendedapplication, the machine may be provided with deployable stabilizerlegs.

A subset of telehandlers mount the cab and boom on a rotatablesuperstructure in order to combine lifting with slewing operations, atthe expense of additional weight and greater height. As these machinesare used principally for lifting, instead of loading, they have a longerwheelbase than conventional telehandlers to accommodate a longer boom,impacting maneuverability. Further, as sight-lines towards the groundclose to the machine are less critical for lifting than for excavating,these are consequently quite poor.

For some lifting operations, particularly those of heavy load, it ismore appropriate to use a crane than a telehandler. Mobile cranes aregenerally provided on a wheeled or tracked base. A boom, often atelescopic boom, is pivotally mounted to the base. Hoists, wire ropes orchains and sheaves are connected to the boom and used for movingmaterials from one location to another. The safety regulations forcranes are often stricter than the safety regulations for telehandlers.

In alternative working operations a worker may need to access anelevated work area, in such cases a mobile elevated work platform (MEWP)may be used. A MEWP generally has a wheeled base with a working armconnected thereto. The working arm carries a platform for a worker. Theworking arm may be for example, a scissor lift or an extensible orarticulating boom. Since use of an MEWP involves working at an elevatedlevel, there are again different technical and safety requirementsimposed on an MEWP compared to those of the previously described workingmachines.

A yet further alternative working machine is a dump truck (also known asa dumper truck). A dump truck is often used for transporting materialfrom one location to another (e.g. a multiplicity of loads from anexcavator bucket). A dump truck has a dump body or a box bed that ispivotable to permit contents of the dump body to be unloaded. A tippingmechanism that is generally actuated by one or more hydraulic cylinders,and in some cases a cylinder and lever arrangement, is used to tip thedump body.

The cost to develop different machines such as those above for differentworking applications is significant. Further, the cost and delay toswitch a production line from one type of machine to another is alsosignificant.

In addition, large assemblies for these machines may be manufactured inone location and the shipped a significant distance to a second locationfor assembly. The shipping cost may high be due to the bulk of theassemblies and the shape thereof, making packing thereof for transportinefficient.

SUMMARY OF THE INVENTION

A first aspect of the invention provides an undercarriage for a workingmachine comprising a main chassis and a subsidiary chassis, wherein themain chassis comprises a mounting arrangement to mount a superstructurethereon and a mounting interface to mount the subsidiary chassisthereon, wherein the subsidiary chassis comprises a mount for an axle.

Providing a main chassis which can be substantially the same across avariety of working machines, may reduce the number of parts and allowsfor a single production line to produce multiple machines therebyreducing cost. The modular arrangement may also save cost by makingtransport of the main and subsidiary chassis more efficient ifmanufactured and assembled at different locations, as it may be possibleto pack more chassis into a given volume for shipping if split intomultiple assemblies.

In one embodiment, the subsidiary chassis further comprises an actuatorto perform a work function.

In one embodiment, the subsidiary chassis comprises a dozer bladearrangement.

In one embodiment, the subsidiary chassis comprises a stabilizer.

Providing the subsidiary chassis with either a dozer blade arrangementor a stabilizer leg arrangement advantageously permits customization ofundercarriage for different applications.

In one embodiment, the actuator is housed within the subsidiary chassis.

Housing the actuator within the subsidiary chassis may advantageouslyimprove visibility of the operator and also may protect the actuatorfrom external collisions.

In one embodiment, the subsidiary chassis comprises a front and a rearend and two side surfaces extending therebetween.

In one embodiment, the length of the subsidiary chassis is a selectedone of at least two subsidiary chassis of different lengths.

Providing more than one length of subsidiary chassis advantageouslypermits customization of undercarriage for different applications.

In one embodiment, a side pod is mounted to the main chassis, the sidepod comprising a drive arrangement including a prime mover.

In one embodiment, the main chassis further comprises an ECU forcontrolling the drive arrangement.

In one embodiment, the mounting arrangement comprises a slew ring tomount a superstructure thereon.

In one embodiment, the main and subsidiary chassis are securedsubstantially permanently to each other.

In one embodiment, the main and subsidiary chassis are releasablysecured to each other.

In one embodiment, the subsidiary chassis further comprises a mountinginterface.

In one embodiment, the mounting interfaces of the main and subsidiarychassis comprise complementary welding surfaces.

In one embodiment, the mounting interfaces of the main and subsidiarychassis comprise a plurality of bores.

In one embodiment, the mounting interfaces of the main and subsidiarychassis are substantially vertical.

In one embodiment, an axle is mounted to the subsidiary chassis.

In one embodiment, a second subsidiary chassis is mounted to the mainchassis.

A second aspect of the invention provides a working machine comprising asuperstructure including a working arm configured so as to be capable ofperforming working operations, and an undercarriage according to thefirst aspect, wherein the undercarriage is mounted to the superstructurevia the mounting arrangement.

A third aspect of the invention provides a method of forming anundercarriage of a working machine, comprising the steps of:manufacturing a main chassis; manufacturing a subsidiary chassis; andmounting the subsidiary chassis to the main chassis.

In one embodiment, the method comprises a further step of selecting fromat least two alternative working machines types which working machinetype the undercarriage is to be incorporated into, and selecting thesubsidiary chassis to be mounted to the main chassis in accordance withthe working machine selected.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1 is a side view of a working machine;

FIG. 2 is a plan view of the machine of FIG. 1;

FIG. 3 is a schematic view of a hydraulic and electronic control systemof the machine of FIG. 1;

FIG. 4 is a side view of a working machine according to an embodiment ofthe present invention;

FIG. 5 is a side view of a working machine according to an embodiment ofthe present invention;

FIG. 6 is an isometric view of a main chassis according to an embodimentof the present invention;

FIG. 7 is an isometric view of a subsidiary chassis according to anembodiment of the present invention;

FIG. 8 is an isometric view of a subsidiary chassis according to anembodiment of the present invention;

FIG. 9 is a side view of a working machine according to an embodiment ofthe present invention;

FIG. 10 is a side view of a working machine according to an embodimentof the present invention.

DETAILED DESCRIPTION General Format

With reference to FIGS. 1 to 3, there is illustrated in somewhatsimplified form a working machine 10 according to an embodiment of thepresent invention. In the present embodiment, the working machine may beconsidered to be a midi excavator (operating weight between approx. 6and 12 metric tons). In other embodiments the working machine may be amini excavator (operating weight between 1.2 and 6 tons). The machinecomprises a base assembly 11 that includes an undercarriage 12. Asuperstructure 14 is linked to the undercarriage of the base assembly bya slewing mechanism in the form of a slewing ring 16. The slewing ring16 permits unrestricted rotation of the superstructure relative to theundercarriage 12 in this embodiment. A cab 30 from which an operator canoperate the working machine is rotatably mounted to the superstructure.A working arm arrangement 40 is rotatably mounted to the superstructureand provided for performing excavating operations.

Undercarriage

The undercarriage is formed from a pair of spaced chassis rails 18 a and18 b extending fore-aft, and typically but not always being parallel, orsubstantially so. The rails provide a majority of the strength of theundercarriage 12. The undercarriage is connected to a ground engagingstructure, which in this embodiment includes first and second driveaxles 20 a and 20 b mounted to the chassis rails 18 a, 18 b and wheelsrotatably attached to each axle end. In this embodiment the second driveaxle 20 b is fixed with respect to the chassis rails 18 a, 18 b, whereasthe first drive axle 20 a is capable of limited articulation, therebypermitting the wheels to remain in ground contact, even if the ground isuneven. The wheels 19 a, 19 b, 19 c, 19 d are typically provided withoff-road pneumatic tires. The wheels 19 a, 19 b, 19 c, 19 d connected toboth axles are steerable via a steering hub 17 a, 17 b, 17 c, 17 d. Inthis embodiment, the wheelbase is 2.65 m, and a typical range is 2.0 mto 3.5 m.

For the purposes of the present application, the fore-aft direction A isdefined as a direction substantially parallel to the general directionof the chassis rails 18 a and 18 b. A generally upright direction U isdefined as a direction substantially vertical when the working machineis on level ground. A generally lateral direction L is defined as adirection that is substantially horizontal when the working machine ison level ground and is substantially perpendicular to the fore-aftdirection A.

In this embodiment a dozer blade arrangement 22 is pivotally secured toone end of the chassis rails 18 a and 18 b, which may be raised andlowered by hydraulic cylinders 21 using a known arrangement, and alsoact as a stabilizer for the machine, by lifting the adjacent wheels offthe ground when excavating, however this may not be provided in otherembodiments.

A stabilizer leg arrangement 24 is pivotally mounted to an opposite endof the chassis rails 18 a and 18 b, which also may be raised and loweredby hydraulic cylinders 23 using a known arrangement, but in otherembodiments this may be omitted.

Drive

In this embodiment, the drive arrangement, including a prime mover andtransmission are housed in the undercarriage 12, where the prime moveris a diesel IC engine 64.

A heat exchanger 66 and cooling fan 68 are housed in the undercarriageadjacent the engine 64. The cooling fan 68 is orientated such that theaxis of rotation Q of the fan extends in a fore-aft direction A,although it may be oriented differently in other embodiments.

A fuel tank 70 provides a fuel supply to the engine 64. A hydraulic tank72 is provided adjacent the fuel tank 70.

The engine 64, heat exchanger 66, cooling fan 68, fuel tank 70 andhydraulic tank 72 are all housed in a region between the axles 20 a and20 b. As can be seen in FIG. 1, the engine 64 is positioned below alevel coincident with a lower extent of the superstructure 14. Indeedthe majority of the engine 64, and in this embodiment the entire engine64 is positioned below a level Q coincident with an upper extent of thewheels 19 a, 19 b, 19 c, 19 d. In the present embodiment the majority ofthe heat exchanger 66, cooling fan 68, fuel tank 70 and hydraulic tank72 are below a level Q coincident with the upper extent of the wheels 19a, 19 b, 19 c, 19 d.

Referring to FIG. 3, in the present embodiment the transmission is ahydrostatic transmission. The transmission includes a high pressureswash plate type hydraulic transmission pump 75 b as well as anassociated charge pump 75 a. The transmission pump in turn is capable ofselectively driving two hydraulic motors 76 and 77. The transmissionpump 75 b has a typical operating pressure of around 350-450 bar (35-45MPa).

The engine 64 is configured to drive the charge pump 75 a, and thetransmission pump 75 b. The pumps 75 a and 75 b are configured to drawhydraulic fluid from the hydraulic fluid tank 72 as required and supplyto the hydraulic motors 76 and 77 via dedicated feed and return hoses(i.e. the flow is essentially closed loop but with hydraulic fluid drawnfrom and returned from the tank 72 as required). In the presentembodiment, the hydraulic motor 76 is positioned towards the dozer bladearrangement 22. The engine 64, hydraulic pump 74, and hydraulic motor 77are positioned towards the stabilizer arrangement 24.

The first hydraulic motor 76 is a high speed swash plate type motorhaving a large displacement range, for example of 0 to 255cm3/revolution, and drives the front axle 20 a in a normal direction oftravel. The output of the motor faces forwards and drives the first axle20 a via a short drive shaft 78 and differential (not shown). The secondhydraulic motor 77 is a relatively low speed swash plate type motorhaving a smaller displacement range for example of 0 to 125cm3/revolution. The low speed motor 77 connects to a second drive shaft80 to drive the second (rear) axle 20 b via a second differential (notshown).

In other embodiments a single hydraulic motor may provide drive to boththe front and rear axles, typically with a two wheel drive/four wheeldrive selector operating a clutch to disengage/engage drive to one axle.

The charge pump 75 a and transmission pump 75 b are positioned adjacentthe engine 64 and are orientated such that an input to the pumps fromthe engine is axially aligned with an output from the engine to thepump.

Arranging the drive arrangement as described in the undercarriage hasbeen found to result a reduction in the volume of components to behoused in the superstructure, in turn resulting in a line of sight overthe right hand rear corner of the machine for an operator having aheight of 185 cm (a 95th percentile male) when seated in the operator'sseat at the left hand side of the machine in excess of 30° (33° in thisembodiment) below the horizontal (compared to around 22° in conventionalmidi excavators of this size). This results in a significant reductionof the ground area around the machine that is obscured by parts of thesuperstructure, thereby improving visibility for maneuvering themachine.

A further advantage of positioning the drive arrangement in theundercarriage, compared to conventional excavators where the drivearrangement is generally positioned in the superstructure is that noise,vibration and harshness (NVH) isolation is improved between the engineand the cab to improve comfort and safety for an operator. In addition,access to the engine, fuel tank, fluid tank, etc. for maintenance andrefueling is at ground level.

Superstructure

The superstructure 14 comprises a structural platform 26 mounted on theslew ring 16. As can be seen in the Figures, the slew ring 16 issubstantially central to the undercarriage 12 in a fore-aft direction Aand a lateral direction L, so as to mount the superstructure 14 centralto the undercarriage. The slew ring 16 permits rotation of thesuperstructure 14 relative to the undercarriage about a generallyupright axis Z.

A rotary joint arrangement 85 is provided central to the slew ring andis configured to provide multiple hydraulic fluid lines, a returnhydraulic fluid line, and an electrical—Controller Area Network(CAN)—signal line to the superstructure 14 from the undercarriage,whilst permitting a full 360° rotation of the superstructure relative tothe undercarriage. The configuration of such a rotary joint arrangementis known in the art.

The platform 26 mounts a cab 30. The cab houses the operator's seat andmachine controls (discussed below).

The superstructure 14 is rotated relative to the undercarriage 12 usinga first hydraulic motor 32 and brake.

The platform further mounts a kingpost 28 for a working arm arrangement40. The kingpost 28 arrangement is known in the art, and permitsrotation of the working arm about a generally upright axis X and about agenerally lateral axis W.

The superstructure further comprises a counterweight 34 for the workingarm arrangement positioned at an opposite side of the superstructure tothe kingpost 28.

Hydraulic Supply

In the embodiment, illustrated in FIG. 3, the engine 64 additionallydrives a main, lower pressure hydraulic pump 74 arranged in series withthe charge 75 a and transmission pumps 75 b. In this embodiment the mainhydraulic pump has an operating pressure of around 250-300 bar (25-30MPa) and is also of a variable displacement type.

The main pump 74 supplies hydraulic fluid to the hydraulic cylinders 50,52, 54, 60, 62 for operating the working arm arrangement via associatedvalves in the superstructure 14 and denoted by the same numeral with thesuffix ‘a’, to a slew brake via a pilot feed valve 83, and to auxiliaryhydraulic fluid supplies for use by certain attachments such a grabsetc. (not shown). The main pump 74 additionally supplies hydrauliccylinders 21, 23 of the dozer blade and stabilizer arrangement via astabilizer/dozer valve 79 in the undercarriage. However, in alternativeembodiments a single pump may be used for supplying hydraulic fluid tothe motors and the hydraulic cylinders. The main pump 74 is further usedto provide hydraulic fluid for air conditioning 93, as illustrated inFIG. 3.

In this embodiment the engine additionally drives a separate pump 74′for the steering system and a fan pump 69 a to drive a cooling fan 69 band a park brake valve 31 a for a parking brake 31 b. These pumps are inthis embodiment gear pumps operable at a lower pressure of around 200bar (20 MPa) and without ECU control.

Further, the charge pump 75 a additionally supplies hydraulic fluid toan axle lock valve 33 a which selectively prevents the articulation ofthe front axle 20 a.

Working Arm

The working arm arrangement 40 of the present embodiment is an excavatorarm arrangement. The working arm arrangement includes a triplearticulated boom 42 pivotally connected to a dipper 44. The triplearticulated boom 42 includes a first section 46 pivotally connected to asecond section 48. A hydraulic cylinder 50 is provided to raise andlower the first section 46 of the boom 42 relative to the kingpost 28about the generally lateral axis W. A further hydraulic cylinder 52 isprovided to pivot the second section 48 of the boom 42 relative to thefirst section of the boom about a generally lateral axis T. A yetfurther hydraulic cylinder 54 is provided to rotate the dipper 44relative to the boom 42 about a generally lateral axis S. A mount 56 isprovided to pivotally mount an attachment to the dipper 44, in thepresent embodiment the attachment is a bucket 58. A hydraulic cylinder60 is provided to rotate the attachment relative to the dipper 44.Alternatively boom cylinder arrangements (e.g. twin cylinders) mayhowever be utilized in other embodiments.

Shown most clearly in FIG. 2, a yet further hydraulic cylinder 62 isprovided to rotate (swing) the working arm arrangement 40 about thegenerally upright axis X. Using a hydraulic cylinder arrangement torotate the working arm arrangement simplifies manufacture and operationof the working machine 10.

Machine Controls

A number of machine control inputs are provided in the cab 30. In thisembodiment the inputs (with the exception of steering and braking) areelectrically transmitted via a CAN bus to one or more superstructureElectronic Control Units (ECUs) 86, incorporating a suitablemicroprocessor, memory, etc. to interpret the inputs to signal thevarious valves for controlling movement of the working arm etc. and/orone or more further undercarriage ECUs 87 to ultimately controlhydraulic functions in the undercarriage, including a stabilizer/dozervalve 79, a fan motor 69 b, park brake valve 31 a, axle lock valve 33 a,main pump 74, transmission pump 75 b, steer mode valve 97.

In alternative embodiments an ECU may only be provided in base assembly(e.g. housed in the undercarriage) and signals from the machine inputcontrols may be sent directly to the ECU(s) 87 in the undercarriageinstead of via the ECU(s) 86 in the superstructure. The electricalconnections for such an arrangement can be routed from the controlinputs to the ECU 87 via the slew ring and rotary joint arrangement.

The control inputs include: joysticks 88 to control operation of theworking arm 40, switches 89 for various secondary functions, a handthrottle 90 to set engine speed for working operations, a foot throttle91 to dynamically set engine speed for roading/maneuvering, and aforward/neutral/reverse (FNR) selector 92 to engage drive in a desireddirection.

Due to the safety-critical nature of steering and braking, the brakepedal and steering are hydraulically controlled by a brake pedal 94 andsteer valve 95 linked to a steering wheel (not shown). Hydraulic fluidfeed is from the dedicated steer pump 74′ via the rotary joint 85 and apriority valve 96, which ensure an appropriate supply of hydraulic fluidis provided to the brake pedal 94/steer valve 95, dependent upon demand.

The steer valve 95 then feeds the steer mode valve 97 in theundercarriage 12, which controls whether the machine is operating infour-wheel steer (off road), two-wheel steer (on road) or crab steer,via another feed through the rotary joint. The steer mode valve thenfeeds hydraulic fluid to appropriate steering cylinders 98, dependentupon the mode chosen.

The brake pedal 94 supplies fluid to service brakes 99 at the wheel endsalso via a feed through the rotary joint. A separate hydraulic fluidfeed from a fan pump 69 a supplies a parking brake valve 31 a as well asthe fan motor 69 b and axle lock valve 33 a under the control of thesuperstructure ECU(s) 86 and undercarriage ECU(s) 87.

In other embodiments, braking and steering may be affected viaelectronic control, provided a suitable level of fault tolerance isbuilt into the system.

High Speed Roading Operation

When operating on road (“roading”) or e.g. maneuvering on a level/hardsurface, speed of movement of the machine 10 is preferred ahead oftraction or torque. Thus, in a first two-wheel drive operating mode, thevehicle operator selects 2WD on a 2WD/4WD selector (not shown),signaling the appropriate superstructure ECU 86, which in turn signalsthe transmission pump 75 b via the undercarriage ECU 87 to permit theflow of hydraulic fluid to the high speed motor 76.

Thereafter, the operator selects forward or reverse from the FNRselector 92, the signal for which is fed through to the transmissionpump 75 b in a similar manner to direct hydraulic fluid therethrough inthe correct flow direction to turn the high speed motor 76, andtherefore the wheels 19 a and 19 b, in the desired direction.

The operator then sets the engine speed using the foot throttle 91 whichin turn drives the transmission pump 75 b at the desired speed. Theundercarriage ECU 87 controls the swash angle of the pump 75 b and highspeed motor 76, resulting in rotation of the high speed motor 76 anddriven rotation of the wheels 19 c, 19 d on the first axle 20 a.

Typically, this enables travel at a maximum speed of around 40 km/h.

Low Speed Operation

For low speed, higher torque, higher traction maneuvering, typically inan off-road location such as a construction site, the operator selects asecond four wheel drive operating mode from the 2WD/4WD selector. Thisin turn signals superstructure ECU 86, which in turn signals thetransmission pump 75 b via the undercarriage ECU 87 to permit the flowof hydraulic fluid to both the high speed motor 76 and low speed motor77.

Thereafter, the operator selects forward or reverse from the FNRselector 92, the signal for which is fed through to the transmissionpump 75 b in a similar manner to determine the direction of flow ofhydraulic fluid into the high speed motor 76 and low speed motor 77.

The operator then sets the engine speed using the foot throttle 91 whichin turn drives the transmission pump 75 b at the desired speed. Theundercarriage ECU 87 preferably controls the swash angle of the pump 75b and high speed motor 76, ultimately resulting in rotation of the highspeed motor 76, low speed motor 77 and drive to the wheels 19 a, 19 b,19 c, 19 d on both the first and second axles 20 a, 20 b at compatiblespeeds.

Typically, this operating mode provides a lower maximum speed foroff-road operation e.g. of 10 km/h or less.

Modular Undercarriage Assembly

Referring to FIGS. 4 and 5, there is illustrated in somewhat simplifiedform a working machine 510 according to an embodiment of the presentinvention. The drive arrangement of the present embodiment can beconsidered to be substantially the same as described above, with thedrive arrangement is housed in the undercarriage assembly 512.

The undercarriage assembly 512 comprises a main chassis 526 having amounting arrangement 532 so as to mount the superstructure 514 thereonvia a slew ring 516 to allow rotation of the superstructure with respectto the undercarriage. In other embodiments, the mounting arrangement 532may be configured so that the orientation of the superstructure is fixedwith respect to the undercarriage 512. The main chassis 526 comprises afront and rear end and two side plates 537 extending therebetween, andwhich act as part of the chassis rails. The front and rear ends eachhave a mounting interface 534 for mounting a subsidiary chassis 528thereon. The mounting interface 534 consists of three bores (notvisible) on flanges at each corner of the front and rear surface, tosecure the subsidiary chassis 528 to the main chassis 526 with bolts 535or other suitable fasteners. The side plates 537 of the main chassis 526are fabricated from sheet steel with suitable cut-outs (not visible) toallow drive shafts, hoses etc. to pass through. In other embodiments,the mounting interface 534 may comprise a surface suitable for weldingthe subsidiary chassis 528 to the main chassis 526 (see FIGS. 6 to 8below).

The subsidiary chassis 528 have a front and rear end and two side plates518′ extending longitudinally therebetween where a mounting interface536 is located at either the front or rear end of the subsidiary chassis528. The mounting interface 536 of each subsidiary chassis 528 are inthe form of flanges with three bores which are complimentary to thebores 534 of the main chassis 526. In other embodiments the number ofbores may be altered as required, and may also be provided on flangesextending transversely on top and/or bottom edges of the main andsubsidiary chassis.

The subsidiary chassis 528 have either a stabilizer leg arrangement 524or a dozer blade arrangement 522 pivotally mounted to an opposing end ofthe subsidiary chassis 528 to the mounting interface 536. The stabilizerleg arrangement 524 or a dozer blade arrangement 522 can be raised orlowered by hydraulic cylinders 523, 521 respectively using a knownarrangement. The dozer blade arrangement 522 may also act as astabilizer for the machine 510, by lifting the adjacent wheels off theground when excavating.

Each subsidiary chassis 528 is connected to a ground engaging structure,which in this embodiment includes one of drive axles 520 a and 520 bmounted to the subsidiary chassis and wheels 519 rotatably attached toeach axle end. The length between the front and rear end of thesubsidiary chassis 528 can be selected to suit the function of theworking machine 510. FIG. 4 shows two short subsidiary chassis 528resulting in a working machine 510 with a relatively short length andshort wheel base, which is suitable for working machines which require asmaller turning circle and to work in confined spaces, such as anexcavator. Conversely, FIG. 5 illustrates a working machine 510 with twolong subsidiary chassis 528′ resulting in a long wheel base which may bemore suitable for working machines requiring a more stable undercarriagesuch as a crane or rotating telehandler. In other embodiments acombination of a long and a short subsidiary chassis may be used.

Referring to FIGS. 6, 7 and 8, an alternative main chassis 626 andsubsidiary chassis 728 are illustrated. The main chassis 626 isfabricated from two metal side plates 637, 638 and a top plate 660 whichis welded to the side plates at their top edges. The top plate 660includes a mounting arrangement 632 in the form of a slew ring locatedsubstantially in the center of the top plate. The main chassis 626further includes two end plates 662 which are bent around the uppercorners and are welded to the side plates 637, 638. The end plates 662extend to meet the edges of the top plate 660 to define a generallyrectangular space for the transmission components.

The main chassis 626 comprises two mounting interfaces 634 defined bythe end plates 662. In this embodiment, the mounting surfaces 634 areconfigured so as to enable a subsidiary chassis 728, as shown in FIGS. 6and 7, be offered up to conform to the mounting surface of the mainchassis 626 and then be welded thereon.

The main chassis 626 has a recess indicated at 642 in one of the sidesurfaces 637 configured so as to enable the output from the engine (notshown) to pass into the main chassis. The side surface 638 also hasmultiple perforations in its surface for the mounting of ancillarycomponents or structural components of a side pod, in which the engineis housed, onto the main chassis or to allow pipework and cabling topass through.

Referring to FIG. 7, the subsidiary chassis 728 has a mountingarrangement indicated generally at 736 which is shaped to conform to thecorresponding mounting arrangement 634 of the main chassis 626 (as shownin FIG. 6) and to be welded thereon.

The subsidiary chassis includes two arm mounting arrangements 748 a and748 b provided at the lowermost point of the surface opposite of themounting arrangement 736. The arm mounting arrangements 748 a, 748 b areeach in the form of a pair axially aligned bores which allow for astabilizer leg arrangement, dozer blade arrangement etc. to be pivotallymounted onto the subsidiary chassis 728 so as to be activated byhydraulic cylinders (not shown) mounted to pivots 770 to perform a workfunction.

The subsidiary chassis 728 has a recess 750 defining an invertedU-channel extending laterally through its side surfaces configured toallow a drive axle (not shown) to be mounted to the chassis. In thisembodiment the subsidiary chassis 728 includes a first 764 and a second(not visible) mounting frame extending between the side surfaces of thesubsidiary chassis. In this embodiment, the mounting frames are weldedto the inside of the subsidiary chassis 728. The drive axle is securedto the subsidiary chassis 728 via a pivot member (not shown) extendingbetween the first and second mounting frame, this arrangement allows thedrive axle to be capable of limited articulation, thereby permitting thewheels to remain in ground contact, even if the ground is uneven.

Referring to FIG. 8, an alternative subsidiary chassis 828 isillustrated. Corresponding components of the figure are labeled 100higher with respect to FIG. 7 and only differences are discussed. Themetal frame of the subsidiary chassis 828 is substantially the same asdescribed in FIG. 7. In this embodiment, a plate 866 is welded to bothsides of the subsidiary chassis so as to secure the plate along therecess 850. The plate 866 includes a number of bores 868 at each end toenable the attachment of a drive axle (not shown), in order to fix thedrive axle with respect to the subsidiary chassis 828 and preventarticulation.

Crane

Referring now to FIG. 9, an alternative working machine 910 is shown, inthis embodiment the working machine is a crane. The working machine 910has a similar undercarriage assembly 912 to that of the working machine510 of FIG. 5, with the long subsidiary chassis. Correspondingcomponents of the figure are labeled with the prefix ‘9’ instead of ‘5’with respect to FIG. 5 and only differences are discussed.

The superstructure 914 is mounted to the undercarriage 912 via a slewring 916 as described previously, such that the superstructure andworking arm arrangement 940 can rotate relative to the undercarriage.

The connected superstructure 914 has a crane working arm 940 in the formof a telescopic boom which may be positioned horizontally in its lowestposition, as illustrated. In the present embodiment, the hoist includesa cable 901 and a winch 902, where the winch is provided at the base ofthe boom. Positioning the motor 957 and the winch 902 at the rear of theboom 940, as opposed to the front, improves lift capacity and forwardstability of the crane.

In such an embodiment the undercarriage 912 has four stabilizer legs 924connected thereto and during a lifting operation the stabilizer legs arefully extended to lift the wheels 919 of the undercarriage off theground.

Stabilizer/Dozer Linkage

Referring to FIG. 10, an alternative working machine 1010 is shown. Thedrive arrangement of the present embodiment can be considered to besubstantially the same as described above, corresponding components ofthe figure are labeled 100 higher with respect to FIG. 8 and onlydifferences are discussed.

In this embodiment the linear actuators in the form of hydrauliccylinders 1021, 1023 are mounted within the subsidiary chassis 1028 andextend out of openings in the subsidiary chassis so as to actuate adozer blade arrangement 1022 or a stabilizer leg arrangement 1024respectively via a linkage 1062. It can be seen that both linkages 1004are substantially identical, despite connecting to differing arms, andcomprise a generally L-shaped lever 1005 pivotally mounted to thesubsidiary chassis 1028 at the apex of the two arms forming the L. Onefree end of the “L” pivotally connects to the hydraulic cylinders 1021,1023 and the other free end pivotally connects to an end of a link arm1006. A second end of the link arm 1006 pivotally connects to the dozerblade 1022 or stabilizer leg 1024. This linkage effectively convertsgenerally horizontal extension and contraction of the cylinders 1021,1023 into generally vertical arcuate movement of the dozer blade orstabilizer legs.

Providing the hydraulic cylinders within the subsidiary chassis 1028minimizes the overall size of the undercarriage and may improvevisibility of the operator. Furthermore, this arrangement will providethe hydraulic cylinders with protection from damage.

Providing a main chassis which can be substantially the same across avariety of working machines, such as a crane, a telehandler or anexcavator, may reduce the number of parts and allows for a singleproduction line to produce multiple machines thereby reducing cost. Themodular arrangement may also save cost by making transport of the mainand subsidiary chassis more efficient if manufactured and assembled atdifferent locations, as it may be possible to pack more chassis into agiven volume for shipping if split into multiple assemblies as describedabove.

Providing a subsidiary chassis which can be substantially the same withthe exception of the drive axle mount may allow for economies of scaleto provide for the lower cost manufacture of the undercarriagecomponents.

Variants

Although the invention has been described above with reference to one ormore preferred embodiments, it will be appreciated that various changesor modifications may be made without departing from the scope of theinvention as defined in the appended claims.

Although the present invention has been described in the context of aparticular machine layout, for which it is considered particularlyadvantageous, certain advantages of the present invention may beachieved if it is used in more conventional machines such asconventional wheeled slew excavators having engines and hydraulic pumpsin the superstructure thereof, or telehandlers, rough terrain cranesetc. having hydrostatic or other types of transmissions. In addition, inother embodiments, the prime mover may be located within either the mainor subsidiary chassis, instead of within a side pod.

In an alternative embodiment, the main chassis may have mounts for anaxle, a hydraulic cylinder and one of a dozer blade arrangement, astabilizer leg arrangement or a tractor-type hydraulic three-pointlinkage. In this embodiment, the main chassis may be configured to mountonly one subsidiary assembly to the main chassis.

In a further alternative embodiment, the main chassis may be configuredso as to define a recess at its front and rear ends (e.g. by havingchassis rails in the form of opposed C-beams). The members may beconfigured so as to enable a subassembly to be inserted into the recessin the main chassis and be releasably secured to the main chassis. Inthis embodiment, the subassembly may be a stabilizer leg arrangement, adozer arm arrangement, a three-point linkage etc. In alternativeembodiments, the subassembly may also mount a drive axle to the mainchassis, where the axle may or may not be fixed with respect to thesubassembly in a similar way to that described in FIGS. 7 and 8.

Alternatively, the main chassis may have structural members, such aslongitudinally extending chassis members protruding from the frontand/or rear surfaces of the main chassis. A subassembly having anactuator to perform a work may be configured to mount over theseextending chassis members and may be able to be (optionally releasably)secured to the main chassis via the chassis members. The subassembly maya stabilizer leg arrangement, a dozer blade arrangement, a three-pointlinkage etc. In this embodiment the axle mount may either located on themain chassis or the subassembly may be further configured to mount anaxle thereon.

The working machine may be operated using manual, hydraulic orelectro-hydraulic controls.

In other embodiments, an alternative transmission arrangement may beused, such as a conventional gearbox, powershift gearbox or torqueconverter gearbox. An alternative prime mover may also be used insteadof or in conjunction with an IC engine, for example an electric motor.

In the present embodiment, the wheels on both axles are steerable (i.e.the working machine is configured for four wheel steer), but inalternative embodiments only the wheels on one of the axles may besteerable (i.e. the working machine is configured for two wheel steer).

1. An undercarriage for a working machine comprising a main chassis anda subsidiary chassis, wherein the main chassis comprises a mountingarrangement to mount a superstructure thereon and a mounting interfaceto mount the subsidiary chassis thereon, wherein the subsidiary chassiscomprises a mount for an axle.
 2. An undercarriage according to claim 1,wherein the subsidiary chassis further comprises an actuator to performa work function.
 3. An undercarriage according to claim 2, wherein thesubsidiary chassis comprises a dozer blade arrangement.
 4. Anundercarriage according to claim 2, wherein the subsidiary chassiscomprises a stabilizer.
 5. An undercarriage according to claim 2,wherein the actuator is housed within the subsidiary chassis.
 6. Anundercarriage according to claim 1, wherein the subsidiary chassiscomprises a front and a rear end and two side surfaces extendingtherebetween.
 7. An undercarriage according to claim 1, wherein a sidepod is mounted to the main chassis, the side pod comprising a drivearrangement including a prime mover.
 8. An undercarriage according toclaim 7, wherein the main chassis further comprises an ECU forcontrolling the drive arrangement.
 9. An undercarriage according toclaim 1, wherein the mounting arrangement comprises a slew ring to mounta superstructure thereon.
 10. An undercarriage according to claim 1,wherein the main and subsidiary chassis are secured substantiallypermanently to each other.
 11. An undercarriage according to claim 1,wherein the main and subsidiary chassis are releasably secured to eachother.
 12. An undercarriage according to claim 1, wherein the subsidiarychassis further comprises a mounting interface.
 13. An undercarriageaccording to claim 12 when dependent upon any one of claims 1 to 11,wherein the mounting interfaces of the main and subsidiary chassiscomprise complementary welding surfaces.
 14. An undercarriage accordingto claim 12, wherein the mounting interfaces of the main and subsidiarychassis comprise a plurality of bores.
 15. An undercarriage according toclaim 1, wherein an axle is mounted to the subsidiary chassis.
 16. Anundercarriage according to claim 1, wherein a second subsidiary chassisis mounted to the main chassis.
 17. A working machine comprising asuperstructure including a working arm configured so as to be capable ofperforming working operations, and an undercarriage according to claim1, wherein the undercarriage is mounted to the superstructure via themounting arrangement.
 18. An undercarriage for a working machinecomprising a main chassis and a subsidiary chassis, wherein the mainchassis comprises a mounting arrangement to mount a superstructurethereon and a mounting interface to mount the subsidiary chassisthereon, wherein the subsidiary chassis comprises a mount for a dozerblade arrangement or a stabilizer leg arrangement.
 19. A method offorming an undercarriage of a working machine, comprising the steps of:a. manufacturing a main chassis; b. manufacturing a subsidiary chassis;and c. mounting the subsidiary chassis to the main chassis.
 20. A methodof forming an undercarriage of a working machine according to claim 19comprising a further step of selecting from at least two alternativeworking machines types which working machine type the undercarriage isto be incorporated into, and selecting the subsidiary chassis to bemounted to the main chassis in accordance with the working machineselected.